Many mobile stations (or “user equipment” (UE)) are now configured so as to be able to obtain access to the Internet (or other IP network) through a variety of access networks. For example, a mobile station may obtain access to the Internet through a non-3GPP defined access network (e.g., a WLAN/WiFi network) and through a radio access network (RAN), such as a 3GPP RAN (e.g., a GSM/EDGE RAN (GERAN), UTRAN, etc.). In the rest of this document we will use Wireless LAN (WLAN) to exemplify a non-3GPP access technology. It should however be understood that other non-3GPP access technologies may be used as well.
When a mobile station accesses the internet using a WLAN access network, the mobile station may make use of a Home Agent (HA), and when a mobile station accesses the internet using a 3GPP access network, the mobile station may make use of a GRPS backbone network, which includes a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN). 3GPP is defining a solution for IP session continuity when a mobile station moves from accessing the Internet through a WLAN to accessing the Internet though a 3GPP RAN. To facilitate this IP session continuity, it has been proposed to collocate the HA function with the GGSN (e.g., provide a GGSN with software for implementing an HA).
One of the main benefits with combining HA and GGSN into a single node is that it is possible to avoid Mobile IP specific signaling and user plane overhead when a mobile station is accessing the Internet via GPRS. This is accomplished by treating the GPRS access as a “home link” for the mobile station. A “Home link” is a specific case for Dual Stack Mobile IPv6 (DSMIPv6) when the mobile station uses an access where the IP address allocated to the mobile station in that access is equal to the Home Address (HoA) allocated to the mobile station by the DSMIPv6 HA. Corresponding “home link” functionality is present also in other Mobile IP variants such as Mobile IPv6 (MIPv6) and Mobile IPv4 (MIPv4). DSMIPv6 is used in the descriptions of the embodiments but it should be understood that also other variants of Mobile IP may be used.
When a mobile station is using GPRS access, DSMIPv6 is not activated and IP access is provided to the mobile station using regular GPRS procedures only. When the mobile station is using WLAN access (e.g., I-WLAN access), the mobile station receives a Care-of Address (CoA) from the Packet Data Gateway (PDG) and connects to the HA function in GGSN/HA using DSMIPv6. The IP address assigned in GPRS (PDP address) is the same as the IP address assigned via DSMIPv6 (Home Address).
With the combined GGSN/HA it is required that the same GGSN/HA entity is selected when the mobile station is using GPRS and I-WLAN. One issue with this is that GGSN selection mechanisms are different from HA selection mechanisms.
GGSN selection in GPRS is done by the SGSN based on an Access Point Name (APN). APN information may be received from the HLR, from the mobile station or be pre-configured in the SGSN. Based on the information received from the mobile station, the HLR or that is preconfigured in the SGSN, the SGSN creates an APN string that is resolved in DNS. In the reply from DNS, the SGSN receives one or more IP addresses to GGSN(s) that support the requested APN.
HA selection for DSMIP6 may be done in different ways. One option specified for I-WLAN mobility is that the mobile station resolves a “HA APN” in DNS. Note that this DNS system is accessible to the mobile station and logically separate from the GPRS core network internal DNS system used by SGSN. In the reply from DNS, the mobile station receives one or more IP addresses to HA(s) that support the requested HA APN.
What is desired are systems and methods for selecting a support node so that the same GGSN/HA entity is selected when a mobile station transitions WLAN access to GPRS access.